So what is this weird beast "Metallica Through the Never"? It's two-thirds orthodox concert flick, one-third wordless sci-fi fright show. For America's biggest metal band, it's an ambitious but garbled attempt to stir up new evil.

Director Nimród Antal ("Kontroll," "Predators") sets up an intriguing premise for "Metallica Through the Never." As the band rages inside a sold-out arena show, a young roadie on assignment gets sucked into a battle among balaclava-clad street gangs, brutal riot cops and at least one horseman of the apocalypse. If you're at all familiar with Metallica's three decades of sinewy riffage and doom-stricken lyrics, it will feel entirely apropos.

As a straightforward concert document, "Through the Never" is excellent. Although the San Francisco-bred band hasn't been at metal's artistic vanguard for years, it remains a stellar live act and one of the last big draws in rock. The performance footage of "Through the Never" is seamlessly stitched from a few tour dates, and Antal's clever staging captures the band's ferocious instrumentalism.

The four members prowl an unusual four-pronged stage in-the-round, showing their individual charismas — drummer Lars Ulrich the curmudgeonly perfectionist, bassist Robert Trujillo the low-slung enforcer, guitarist Kirk Hammett the baked-looking warlock. The 3-D is generally tasteful (even if you get enough of singer James Hetfield's chest hair to feel as if you have to pick it out of your teeth), and the song selections — "Hit the Lights," "Ride the Lightning," "Master of Puppets" — will earn devil-horns from old thrash-metal vets and festival novices alike.

The problem is that Antal and Metallica took two different movies — a fine live-band document and a supernatural end-of-days romp — and smashed them together to make both of them more boring.

Dane DeHaan ("The Place Beyond the Pines") is convincing as Trip, the weary, devoted young Metallica roadie set upon by thugs and demons while retrieving a bag belonging to the band (one can't imagine Kings of Leon or the Black Keys commanding such loyalty today). Antal and the film's cinematographer, Gyula Pados, occasionally wring some real dread out of the scenario. The grim shots of public hangings could make Burzum's church-burning singer Varg Vikernes flinch.

But like a blast-beat metal drummer lagging behind his band, the dialogue-free fictional segments and the live concert footage don't seem to have much to do with each other.

Sometimes the problems are metaphysical — does Metallica know the apocalypse is happening outside its arena show? Is Trip fighting the street rioters or the cops or the evil horseman, who seems to be killing everyone simultaneously? And the answer to that movie-driving question of "What's in that infernal bag Trip's carrying anyway?" is a jerky cop-out.

But mostly, the flaws are structural. Just when you get comfy watching a long, pulverizing take on "…And Justice for All," the film suddenly veers to Trip self-immolating in an alleyway. Then back to the band doing "Nothing Else Matters," followed by Trip's city-destroying showdown with the dark rider on the roof of the arena.

All this disrupts the Metallica show inside only briefly. And to think the Stones barely made it through Altamont.

If Antal and the band had a bit of self-awareness, they could have made a kind of "Heavy Metal Parking Lot" meets "Quadrophenia" and "Evil Dead" — a brawny, campy genre movie that takes Metallica-ness in wild new directions, while showcasing the group at its onstage best. The lean and menacing Metallica circa-1983's "Kill Em All" would have loved that movie.

Instead, "Metallica Through the Never" feels more like the group as seen in 2004's droll band-in-couples-therapy documentary "Some Kind of Monster" — a little confused, unsure of itself and losing the plot despite having powerful talents at its disposal. If only this master of puppets had a tighter grip on the strings.